Containers for foods such as cup noodles and puddings are required to have shape retainability—an ability with which they can retain the shape in the lid open state and the shape in the lid closed state. Aluminum and other metals have heretofore been employed as the lid materials for such food containers. However, studies have been made for shape-retaining resin films because of disadvantages of aluminum, such as time-consuming separate disposal and inapplicability to products for microwave oven use, where water or other liquid is poured in the container for cooking.
As the shape-retaining resin films, uniaxially-stretched polyethylene films have been proposed (see, e.g., Patent Literature 1). In addition to usage as shape-retaining films, it is recognized that uniaxially-stretched polyethylene films are used as easy-tearing films for food packaging (see e.g., Patent Literature 2). In some applications, additional functional layers such as printable films and/or heat sealing layers are laminated onto these container lid materials and packaging films.
Packaging bags for powdery foods, retort foods, snacks and other foods as well as packaging bags for detergents and other agents are required to exhibit such shape retainability that allows for content removal in a self-standing position or air-tight sealing by simply folding over on itself at the open end.
As the shape-retaining bags, packaging bags have been proposed that include aluminum foil serving as a shape retainer. For example, gusset bags have been proposed that include a multilayer film in which aluminum foil is sandwiched by multiple resin layers (see Patent Literature 3). Gusset bags that exhibit enhanced shape retainability at the open end have also been proposed in which plastically deformable thin bars are incorporated into the sides of the bag that fold in to form a “gusset” (see Patent Literature 4).
As shape-retaining resin fibers, resin fibers have been proposed that are prepared by micro-slitting of uniaxially-stretched polyethylene films having a glossy layer laminated thereon (see Patent Literature 5).
As structures for diffusing heat generated from such heat sources as electric parts, structures for reducing thermal contact resistance have been known in which a heat-conductive silicone grease or a flexible, sheet-shaped heat-conductive silicone rubber (heat-conductive sheet) is disposed between the heat source and heat dissipator such as a heat sink.
Heat-conductive sheets that exhibit enhanced thermal conductivity have been known in which metals, ceramics, carbon fibers, etc., that exhibit high thermal conductivity are incorporated into the sheet. For example, heat-transfer sheets have been proposed that are prepared by mixing silicone gel with metal oxide or boron nitride to provide grooves on their surface (see, e.g., Patent Literature 6). The heat-transfer sheets are claimed to be able to absorb thermal expansion by being deformed upon pressure bonding between the heat-generating elements and heat dissipator.
Also proposed are heat-conductive sheets with enhanced strength for good operability. Examples include heat-conductive sheets that include a composite layer of a strength-retaining layer composed of silicone rubber mixed with heat-conductive filler, and a deformable layer composed of flexible silicone gel containing heat-conductive filler; and low-hardness silicone rubber sheets that include a silicone rubber layer and a reinforcement layer (see, e.g., Patent Literatures 7 and 8).
On the other hand, in electronic devices that are being increasingly downsized and slimmed down, e.g., laptop computers and cellular phones, due to limited space directly above heat sources such as CPU and ICs, heat diffusion needs to be effected by providing a heat dissipator at a position remote from the heat sources. In order to allow heat to be conducted from the heat sources as far as to the heat dissipator, they are coupled together with a heat-conductive sheet.